Since oil was found under the North Sea in the mid 1960's, oil production now plays an important part in Norwegian economy. A major oil field is Ekofisk, between Norway and Britain (Figure 1). The Alexander Kielland, one of the rigs at Ekofisk, was a mobile platform of the pentagon type, floating on 5 columns, 150 nautical miles of f the Norwegian coast. It was developed and built as a drilling rig, but was used as an accommodation platform since delivery in July 1976. OnMarch27,1980, the Alexander Kielland rig lay at anchor on the Ekofisk field, close to the production platform EDDA.